|“Vietnam Lagoon at Dawn,” Public Domain Image.|
It seems counterintuitive that exposing oneself to bright light could actually help someone sleep better. However, a quick review of the biological processes which lead to sleep may clarify how light has a relationship to sleep.
The sleep process itself is informed by two separate biological functions:
- Sleep-Wake Drive: This is the process that is part of our homeostatic drive. It relates to the daily rise and fall in our neurochemical makeup which informs us when we are tired or ready to wake up. The sleep-wake drive is regulated by the part of the brain which also regulates our other drives: sex, thirst, hunger, etc. When you have enough sleep, your sleep drive wanes and your wakefulness drive kicks in, and vice versa.
- Circadian Rhythms: These are biological rhythms built not only inside our brains but in specific organs and even within our cells. They are informed by our exposure to certain cues in our environment, especially light. Our bodies, like all living things, are “entrained” to the light-dark cycles of the earth and so our sleep cycles are equally informed by the rising and setting of the sun. It is the circadian clock inside the pineal gland which produces melatonin as the light of the day wanes. Melatonin serves to prepare the body and brain for sleep. With enough light exposure during the evening, the pineal gland will sense the light and stop producing melatonin, thus halting the drive to sleep.
Together, these two mechanisms regulate our sleeping patterns. When such patterns fall out of “entrainment,” it results in a dysfunction of sleep phasing. This leads to either falling asleep later and sleeping in, which can be impractical or problematic for many, or falling asleep too early and waking too early, which can also be problematic.
Some people do not have consistent sleep cycles at all because of circadian rhythm dysfunction; their sleep-wake drives kick in at extremely impractical times (like 3pm for bedtime and 1am for rise time), making life very hard for them if they need to attend classes, hold a job or make appointments. And to make matters worse, some people have sleep cycles that continuously shift, meaning they can’t guess just when their body will demand sleep.
Light therapy, also known as phototherapy or heliotherapy, serves those with problematic shifting in their sleep schedules. Intentional exposure to specific kinds of light–lamps, photo boxes, even wearable technology–for a certain amount of time and, often, at a very specific time of day, can help “re-entrain” that person’s rhythms so they more closely mimic the sleep patterns they want.
An example: A person who struggles with late-afternoon sleepiness and finds it challenging to stay up past 6pm may try using exposure to light to delay early melatonin production in the brain and “reset” their circadian rhythms over a period of time until they become “re-entrained” to a more normal sleeping pattern.
Another example: A person who struggles with insomnia may try avoiding all exposure to bright and/or blue spectrum light (which is emitted by all electronic devices with a screen, including pads, phones, handheld game, computers, laptops, and TVs) after the sun goes down in order to encourage more melatonin production. Then, they try to sleep and set their alarm for a reasonable morning rise time and, upon waking at the sound of the alarm, they can expose themselves to the bright and/or blue spectrum light for a period of 15 or 20 minutes to stimulate wakefulness and force their bodies to “reset” to an earlier schedule. That earlier schedule, combined with no napping, can help generate a stronger sleep drive that helps them to fall asleep at a reasonable time at night.
A third example: People who suffer from jet lag find that using full spectrum light following a very specific schedule while traveling, before traveling and after they come home can help to reduce the side effects of crossing multiple time zones, which can be problematic for circadian rhythm function.
A final example: Third (“graveyard”) shift works may find that using a light box during a specific time during their evening shift can help them to remain awake and focused.
These are nonspecific examples and do not constitute treatment that’s “one size fits all.” All of these potential therapies do not happen with just one day-night use; this course of therapy must be repeated according to a specific schedule for it to work, and for some people who are very challenged by circadian rhythm dysfunction, it could take a long time to correct or may not even work at all.
A person who is interested in using light therapy for sleep problems would be best advised to work with a medical professional trained in this kind of treatment if they have been diagnosed with a circadian rhythm disorder or insomnia or jet lag. Light therapy can exacerbate some health conditions and can interfere with certain kinds of drug therapies.
About the delivery system
Most light therapy uses something called a “light box,” or a bright full-spectrum lamp or a wearable headpiece garment to deliver up to 10,000 lux (units of light) across a specific distance, making these light delivery systems much brighter than normal household lighting.
Keep in mind that, however, that on an overcast winter’s morning, if the sun is up, the brightness of sunlight even under these conditions is far brighter than interior manmade lighting, including these devices, and it is the more natural resource of light that human brains and bodies have been “syncing” to for millennia. Instead of using a light therapy delivery system, some people may simply benefit from a half-hour walk outside at the same time in the morning to get “re-entrained” to their circadian rhythms.
Are there risks?
Using a delivery system for light therapy requires that patients not stare directly at the light, and that they remain a certain specified distance from the light for a specified period of time and at a specific time of day in order to achieve maximum results.
People with sleep problems who are not yet diagnosed should resist buying and using a light delivery system without first meeting with a clinician to discuss diagnosis of their problems first. Many sleep problems require a diagnosis first; you would not want to invest in special lights if they were not the proper treatment for your sleep problem and, in fact, could worsen your condition. If light therapy is indicated as a treatment option by your doctor, only then should you use it, and only for the duration and timing prescribed by your physician. If prescribed, purchases of light therapy equipment may even be covered by insurance, but not so if you are self-treating without the guidance of a doctor.
Side effects for light therapy, even for those prescribed it by a physician, include headache, nausea, eye irritation and jitters. Those with mood disorders will require special attention as light therapy can agitate their conditions. Light therapy devices should be built to filter out ultraviolet (UV) rays; if you purchase such a device, please ensure this critical safety feature has been built into your device. Exposure to concentrations of UV rays can be dangerous to both the skin and eyes.
Circadian Sleep Disorders Network || Light Therapy
Columbia University || Q&A on Bright Light Therapy
Mayo Clinic || Light Therapy
National Sleep Foundation || Light Therapy for Insomnia Sufferers
News-Medical.net || What is Light Therapy?
.profita || Lightwear: An Exploration in Wearable Light Therapy for Seasonal Affective Disorder
Sleep Education || Bright Light Therapy
A friendly reminder that links to websites offering products does not imply endorsement by SleepyHeadCENTRAL.com.
SleepyHeadCENTRAL strongly encourages people with ongoing sleep health problems to approach a medical professional to determine appropriate differential diagnoses and treatment. This post, like all other posts on SHC, is not intended to substitute for medical advice.